Syrian Prime Minister Wael al-Halqi escaped an assassination bid on Monday, surviving a blast against his convoy in Damascus, in the latest attack on top members of President Bashar al-Assad's regime.

The attack came as Republican lawmakers in the United States stepped up calls for American action after claims Assad's regime used chemical weapons against its population during its battle against an uprising now in its third year.

Syrian state television said Halqi was unharmed in the blast in the Mazzeh district of the capital.

"The terrorist explosion in Mazzeh was an attempt to target the prime minister's convoy and Dr. Wael al-Halqi was unharmed," state television reported, adding that the blast had caused casualties.

The Syrian Observatory for Human Rights watchdog said one of Halqi's bodyguards had been killed.

"A second bodyguard and the driver are in critical condition," Observatory director Rami Abdel Rahman told AFP, adding that the convoy appeared to have been targeted by a remotely-detonated car bomb.

State television said the explosion happened near a public garden and a school in the neighbourhood, a well-secured district that is home to embassies, government buildings, intelligence facilities and several political figures.

"I was walking in the street when suddenly there was a very powerful explosion and I saw a car burning and people running," a young man told AFP at the scene.

"I heard glass shattering," he added, saying he had tried to hide for fear a second explosion would follow.

An AFP photographer at the scene said several vehicles were destroyed in the blast, including a bus burned out by the explosion. The windshields of other cars nearby were also blown out.

State television al-Ikhbariya broadcast footage of Halqi attending a government meeting and giving a statement afterwards, but it was unclear whether the footage was from before or after the attack.

A news bulletin quoting Halqi saying "these types of attacks are nothing but proof of the discouragement and despair of the terrorist groups as a result of the actions of the Syrian army."

Halqi, who was appointed prime minister in August 2012 after his predecessor Riad Hijab defected to the opposition, is the latest in a string of regime officials to be targeted for assassination.

In July 2012, a suicide bomb attack killed Syria's defence minister and deputy defence minister and left the country's interior minister seriously wounded.

The capital has also been targeted in several major bombings, including an explosion on April 9 in the centre of the city which killed at least 15 people.

The attack against Halqi came as US Republican lawmakers piled pressure on the administration to take action over Syria's alleged use of chemical weapons.

But despite the criticism of President Barack Obama's failure to do more, there was little agreement on precisely how the United States should act.

"We need to get involved. And there's a growing consensus in the US Senate that the United States should get involved," Republican Senator Lindsey Graham said on CBS's "Face the Nation."

But he acknowledged that "Syria is difficult," and any action would be risky.

And international consensus remains elusive, with Russia standing by the Syrian regime and warning Monday that a search for weapons of mass destruction should not be used an excuse to oust Assad.

"There are governments and outside players that believe that all means are appropriate to overthrow the Syrian regime," Russia Foreign Minister Sergei Lavrov said in Moscow.

"But the subject of using weapons of mass destruction is too serious -- it should not be joked around with."